Documentation

Given a start direction d and a sweep angle s, arc d s is the
path of a radius one arc starting at d and sweeping out the angle
s counterclockwise (for positive s). The resulting
Trail is allowed to wrap around and overlap itself.

Given a radus r, a start direction d and an angle s,
arc' r d s is the path of a radius (abs r) arc starting at
d and sweeping out the angle s counterclockwise (for positive
s). The origin of the arc is its center.

Given a start direction d and a sweep angle s, arcT d s
is the Trail of a radius one arc starting at d and sweeping out
the angle s counterclockwise (for positive s). The resulting
Trail is allowed to wrap around and overlap itself.

bezierFromSweep s constructs a series of Cubic segments that
start in the positive y direction and sweep counter clockwise
through the angle s. If s is negative, it will start in the
negative y direction and sweep clockwise. When s is less than
0.0001 the empty list results. If the sweep is greater than fullTurn
later segments will overlap earlier segments.

arcBetween p q height creates an arc beginning at p and
ending at q, with its midpoint at a distance of abs height
away from the straight line from p to q. A positive value of
height results in an arc to the left of the line from p to
q; a negative value yields one to the right.